The present invention relates to the field of catheterization of lumen within the human body, particularly vasculature. Even more particularly, the invention will have application to the manufacture and construction of balloon catheters used in angioplasty.
Angioplasty procedures have gained wide acceptance as an efficient and effective method for treating certain types of vascular diseases. In particular, angioplasty is widely used for stenoses in the coronary arteries, although it is also used for the treatment of stenoses in other parts of the vascular system. The use of core members to provide rigidity and pushability for catheters is well known, and the incorporation of such core members is discussed, for example, in U.S. Pat. No. 5,921,958, entitled Intravascular Catheter with Distal Tip Guide Wire Lumen, which is hereby incorporated by reference.
The most widely used form of angioplasty makes use of a dilatation balloon catheter to treat a stenosis and thereby reestablish an acceptable blood flow through the artery. The dilatation catheter includes an elongated tubular shaft and an inflatable balloon carried at a distal end of the shaft. In operation, the catheter is inserted through a guide catheter which has been previously introduced into a patient""s vascular system from a location remote from the heart (e.g., femoral artery). The proximal end of the guide catheter remains outside the patient while the distal end of the guide catheter is positioned at the coronary artery ostium. A dilatation catheter is introduced into the proximal end of the guiding catheter and advanced to the distal end of the guide catheter. Then, by using fluoroscopy, the physician guides the dilatation catheter the remaining distance through the vascular system until the balloon is positioned across the stenosis.
The balloon is then inflated by supplying fluid under pressure, through an inflation lumen in the catheter, to the balloon. The inflation of the balloon causes a widening of the lumen of the artery to reestablish acceptable blood flow through the artery. After a short inflation period (e.g., 30-90 seconds), the balloon is deflated and the arterial treatment evaluated to determine whether the procedure has reestablished an acceptable blood flow. The evaluation is conducted by introducing a radiopaque dye solution into the artery via the guiding catheter, and then observing the dye flow using fluoroscopy. If necessary, the dilatation procedure is repeated with the catheter balloon being re-inflated. In procedures in the peripheral vessels (vessels other than coronary vessels), a guide catheter may not always be used.
The placement of the dilatation balloon across a stenosis in a coronary artery can be a difficult procedure. Movement of the elongated dilatation balloon catheter (e.g., 135 cm) is achieved by manual manipulation of its proximal end outside the patient. The ability of a catheter to bend and advance through the vasculature is commonly referred to as the xe2x80x9ctrackabilityxe2x80x9d of the catheter. xe2x80x9cPushabilityxe2x80x9d refers to the ability of the catheter to transmit the longitudinal forces applied by the physician along the catheter shaft to advance the distal end of the catheter through a coronary artery to and across the stenosis. Preferably, a catheter has a low profile, and is relatively trackable and pushable.
One common type of dilatation catheter has a guide wire lumen extending through the catheter so that a guide wire can be used to establish the path through the stenosis. The dilatation catheter can then be advanced over the guide wire until the balloon on the catheter is positioned within the stenosis.
In a catheter design where the guide wire does not extend through the catheter balloon, it is important that the catheter structure provide sufficient rigidity along the catheter shaft and through the balloon (all the way to the distal tip of the catheter where the guide wire lumen is located), so that the catheter has the necessary pushability. A core member helps provide this rigidity and pushability. On some catheters, the core member may provide axial rigidity to the entire distal shaft section. On many catheters, particularly balloon catheters, the core member serves a strain relief function as well. The core member reduces kinking of the catheter lumen, such as the inflation lumen in a balloon catheter, which might otherwise occur due to a change in flexibility between a relatively stiff section of tubing, to that of a relatively flexible distal shaft portion.
Core members are typically affixed at the proximal end of the catheter to the catheter hub or manifold. They are affixed either by being embedded in the material from which the hub is formed at the time the hub is manufactured, being affixed with a solder or braze, or being embedded in a mass or glob of cyanoacrylate, epoxy, resin, or other adhesive affixed to the inner wall of the hub. These latter methods tend to complicate the manufacture of the catheter, as either the core member must be incorporated into the hub molding or machining, or else the adhesive must be added to the hub after the hub is formed. Correct placement of the core member adhesive within the hub lumen is a relatively delicate manufacturing procedure which may lead to errors and rejection of catheters under quality control standards. Furthermore, some of these methods of affixing the core member may not sufficiently bond the core member to the hub for all applications or situations.
The present invention pertains to an intralumenal catheter with a core member extending from a proximal hub and through some portion of a shaft distal to the hub. Fixation of the core member into the hub lumen is accomplished in a way that is easier to manufacture than prior methods of securing the core member. The present invention may increase the reliability of the production process, in addition to making the core member more securely fixed in the hub. A catheter of the present invention may also have an inflatable angioplasty balloon, or other devices for reducing or ablating a stenosis, such as an atherectomy-type cutter, a laser device, a water jet device, or sonic or ultrasonic therapeutic devices. The present invention may also be used with other interoperative devices such as drug delivery devices, ultrasonic imaging devices and perfusion devices.
One embodiment of the present invention is a catheter with a flexible, elongate tubular shaft. This shaft has a lumen throughout, and has a proximal and a distal end. A hub with an inner lumen is attached to the proximal end of the shaft. A core member, which runs though at least a portion of the catheter shaft, extends proximally into the hub lumen, and is secured within the lumen. While the core member is substantially in the center of the lumen when entering the distal end of the hub, proximally to this the core member contacts the inner wall of the hub lumen of the hub at two or more points, traversing the hub lumen between points of contact with the inner wall of the hub.
Moving along the core member from a distal opening of the hub to a proximal opening of the hub, the core member at some point is angled so as to gradually extend out from the center of the lumen and contact the inner wall of the hub lumen. After contacting the inner wall of the lumen, the core member is again angled so as to extend to another point on the hub lumen inner wall, such point located proximally from the first point of contact with the hub lumen, but not located on a longitudinal line on the hub lumen inner wall that crosses through the first point of contact. In reaching the second point of contact with the hub inner wall, therefore, the core member may cross substantially over the center of the hub lumen when viewed radially. The core member may then be again angled to contact yet another proximally located point on the hub inner wall. This point, proximal to the first and second points of contact, may be on a longitudinal line on the hub inner wall that crosses through the first point ofcontact, or may be another point on the hub lumen inner wall that is closer to the proximal end of the hub than were the prior points of contact.
The core member is bent or formed so as to zigzag within the lumen of the hub, contacting the walls of the hub in at least two points. The core member is bent or formed in a manner that, if the core member is not in the hub, the core member will spring or expand to a zigzag shape that is slightly wider than the hub lumen, so that upon placement of the core member within the hub lumen, the core member is tension-fit or friction-fit within the hub lumen. In a preferred embodiment of the present invention, the tension caused by the tendency of the core member to expand is such to provide a snug fit and to secure the core member within the hub. In this embodiment of the present invention, the core member may be formed into the desired angled shape using multiple methods or techniques. The core member may be molded, cast, or rolled in the desired shape, or it may be bent or folded after the initial formation of the core member. In either case, in a preferred embodiment, the width of the angled portion of the core member, prior to insertion, is greater than the inner diameter of the hub lumen at least to an extent necessary so that the core member will be secured within the hub when placed in the hub.
When one embodiment of the present invention is viewed axially, i.e., through the hub lumen, the core member zigzag pattern will lie substantially on a plane. In other words, the points of contact between the core member and the hub inner wall lie substantially along two opposite longitudinal lines on the inner wall of the hub lumen. Viewing the core member axially, the angled portions of the core member other than those closest to the viewer may be blocked by the core member angles which are closest to the viewer. However, other embodiments of the present invention are possible, including an embodiment in which the core member, either proximally or distally to a point of contact with the hub inner wall, may traverse the inner hub lumen to make contact with the hub inner wall at a point which is not located on a longitudinal line on the inner wall of the hub which is directly opposite, vis-à-vis the central lumen axis, a longitudinal line passing through a prior point of contact. Alternately stated, when the core member is viewed axially, or xe2x80x9cend onxe2x80x9d through the hub lumen, the core member may appear to form the shape of a star, an xe2x80x9cNxe2x80x9d shape, or any other shape or irregular pattern not reflecting formation on a single plane. In an alternative embodiment incorporating a non-planar anchor configuration, the core member may be formed into a conical or cylindrical helix, contacting the inner wall of the hub more or less continuously along a length of the core member anchor section.
In contrast to core member securement systems of the prior art, the present invention provides for improved and simplified manufacturing processes, and does not require that the core member be molded into the hub wall, or glued to the hub wall. Morever, unlike the present invention, prior methods of core member securement may significantly impede flow of fluid through the hub lumen when the hub lumen is needed for fluid communication.
In a preferred embodiment of the present invention, a catheter has a core wire anchored in accordance with the above embodiment, but in addition, the hub lumen is in fluid communication with the shaft lumen, allowing for delivery of balloon inflation media, such as saline, or other fluids, dyes, or pharmacological material that must be delivered to or through the distal end of the catheter. The catheter may also be capable of conveying fluid material from the distal to the proximal end where the necessary pressure differential, i.e., suction, holds. An embodiment of the present invention incorporates a flexible strain relief sheathing, surrounding the catheter shaft distal to the area of the hub, but in close proximity to the hub, to further prevent crimping and to help prevent a degree of bending that may damage the shaft in the area where it meets the hub. The strain relief is flexible, but not as flexible as the shaft in the area distal to the hub. In a preferred embodiment, the flexible strain relief becomes more difficult to flex as it is flexed, and becomes very difficult to flex as it approaches a degree of flexion wherein the shaft surrounded by the strain relief is near its limit of flexion, i.e., at a point where it is in danger of kinking or folding.
An embodiment of the present invention discloses a method of manufacture and attachment of the core member within the hubs. Under this embodiment, the core member is first formed into a zigzag or spiral pattern disclosed in previously discussed embodiments of the invention. In various embodiments, this formation may be effected by molding the core member into the desired shape, or by bending or pressing the core member to the desired shape, including by the use of a peg template, a crimping press, or another suitable device. Following the formation of the core member into a zigzag or spiral pattern, the so-formed end of the core member is inserted and press fit into the hub lumen with sufficient force to secure the core member within the hub lumen, but in a preferred embodiment, without such force that will substantially bend or crimp the core member further. In an alternative embodiment of the present invention, the distal end of the core member may be pushed though the proximal end of the hub lumen, and after the distal end of the core member is accessible at the distal end of the hub lumen, the core member may be pulled through the hub lumen until the angled proximal end of the core member becomes fixed within the hub lumen. Preferably, the proximal tip of the core member will be pointed so as to embed into the inner wall of the hub lumen, thus further securing the core member within the hub.